libftdi Archives

Subject: Re: write/read syncronization

From: Uwe Bonnes <bon@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
To: libftdi@xxxxxxxxxxxxxxxxxxxxxxx
Date: Thu, 4 Feb 2010 13:58:25 +0100
>>>>> "Igor" == Igor Nikitin <igor.nikitin@xxxxxxxxxxx> writes:

...
    Igor> The question is how to force the immediate reply to have

Try to understand USB packets and how the FT stuffs these packets and the FT
latency.

The FT fill up a buffer and sends it out when its full  or when the latency
elapses. Set the latency low and sleep shortly between the 
ftdi_write_data() and ftdi_read_data()

    Igor> The other question is why does the very first message disappear?
    Igor> Restarting test program again and again, I see that the first
    Igor> "one" is almost always missed, not appearing in further output.

I don't know. Maybe the uC is not out of reset? Maybe the FT takes some time
to setup?  What happens if you loopback tx/rx at the FT232 without the uC
...
    Igor> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    Igor> "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd";>

Please, no HTML in mail.


-- 
Uwe Bonnes                bon@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Institut fuer Kernphysik  Schlossgartenstrasse 9  64289 Darmstadt
--------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------

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